<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <link rel="stylesheet" href="http://at.alicdn.com/t/c/font_4156699_i9rfozb6ac.css">
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      width: 100vw;
      height: 100vh;
      background: linear-gradient(to bottom, skyblue, #003462);
      display: flex;
      justify-content: center;
      align-items: center;
    }



    .searchBar {
      width: 60px;
      height: 60px;
      background-color: #fff;
      box-shadow: 0 0 10px rgba(0, 0, 0, .4);
      border-radius: 60px;
      position: relative;
      overflow: hidden;
      transition: .5s;
    }

    .icon {
      width: 60px;
      height: 60px;
      display: flex;
      justify-content: center;
      align-items: center;
      cursor: pointer;
    }

    .icon i {
      color: dodgerblue;
      font-size: 30px;
    }

    .textInput {
      width: 320px;
      height: 60px;
      display: flex;
      justify-content: center;
      align-items: center;
      background-color: blue;
      position: absolute;
      top: 0;
      left: 60px;
    }

    .textInput input {
      width: 100%;
      height: 100%;
      border: none;
      outline: none;
      font-size: 18px;
    }

    .clear {
      width: 15px;
      height: 15px;
      position: absolute;
      right: 22%;
      top: 50%;
      transform: translateY(-50%);
      cursor: pointer;
      display: flex;
      justify-content: center;
      align-items: center;
    }

    .clear i {
      color: #999;
    }

    .goBtn {
      width: 12%;
      height: 60%;
      position: absolute;
      top: 20%;
      right: 0;
      border-radius: 8px;
      outline: none;
      border: none;
      color: #fff;
      box-shadow: 0 0 2px rgba(0, 0, 0, .4);
      background: linear-gradient(skyblue, deepskyblue);
      cursor: pointer;
    }

    .changeWidth {
      width: 400px;
    }
  </style>
</head>

<body>

  <div class="searchBar">
    <div class="icon"><i class="iconfont icon-sousuoxiao"></i></div>
    <div class="textInput">
      <input class="inp" type="text" placeholder="请输入搜索关键字">
      <button class="goBtn">go</button>
      <div class="clear"><i class="iconfont icon-close"></i></div>
    </div>
  </div>

  <script>
    // 1. 获取元素
    let searchIcon = document.querySelector(".icon")
    let clearIcon = document.querySelector(".clear")
    let searchBar = document.querySelector(".searchBar")
    let inp = document.querySelector(".inp")

    // 2. 点击，切换类 => 改宽实现展开
    searchIcon.addEventListener("click", () => {
      searchBar.classList.toggle("changeWidth")
    })
    // 3. 点击清空
    clearIcon.addEventListener("click", () => {
      inp.value = ""
    })
  </script>
</body>

</html>